1. Field of the Invention
The present invention relates to the technical field of image processing and, more particularly, to a de-interlacing system.
2. Description of Related Art
Conventional television (TV) signals are usually interlaced scan signals due to the limit of display technique. By scanning odd and even rows at different time, the still frame resolution and the motion continuity can be concurrently held at a limited horizontal scan rate. However, when the original content of a video signal is of a film signal, a progressive scan frame is typically divided into two interlaced scan fields, which is referred to as a 2:2 pull down, since a film is obtained by a progressive scan shoot. If a TV signal has different field and frame rates, a different field repetition such as a 3:2 pull down is used in conversion.
Due to the advance of display technology, the screen for current televisions or computers mostly uses a progressive scan manner. Accordingly, a de-interlacing is used to convert the signal from an interlaced scan to a progressive scan. For a non-film signal such as a video signal, the de-interlacing typically makes use of a motion adaptive de-interlacing (MADI) or a motion compensated de-interlacing (also known as motion estimation and motion compensation, MEMC) to produce the progressive scan signal. The MADI technique includes a motion detection to use a spatial interpolation to thereby produce un-transmitted fields for the motion image parts and produce the final progressive scan signal by directly combining the different field signals at tandem time for the still image parts. The MEMC technique uses a motion estimation to find a motion vector and performs a motion compensation according to the field time to thereby produce the un-transmitted field signals.
The de-interlacing for a film signal includes an inverse pull down and a motion compensation. The inverse pull down detects field signals corresponding to the same frame and combines them into the frame. The motion compensation uses a motion estimation and compensation and increases the frame rate.
Current de-interlacers are typically classified into those applying the MADI technique to a non-film signal and the pull down to a film signal, and those applying the MEMC technique to the non-film and film signals.
However, there are some disadvantages on the two de-interlacing techniques. The MADI technique can gain a steady representation for a non-film signal by enhancing a spatial slant low angle interpolation to smooth the motion edges, but for a film signal, the motion judder produced at a lower frame rate cannot be overcome even the inverse pull down can restore an original progressive scan image. The MEMC technique can use the motion compensation to interpolate a frame at a middle time point to thereby reduce the motion judder in a film signal, and increase the vertical resolution of a motion object in a non-film signal. However, the technique can easily present fine horizontal lines in the non-film signal due to the odd and even field differences after the compensation.
Therefore, it is desirable to provide an improved de-interlacing system to mitigate and/or obviate the aforementioned problems.